Glycolipids in a cultured human teratocarcinoma cell line (2102Ep) were investigated. The major glycolipids in these cells are globoseries glycolipids having the following structures: (formula; see text) Synthesis of these structures by serial addition of galactose, fucose, and N-acetylneuraminic acid to globoside (Gb4) in this teratocarcinoma is obvious, although further elongation of Gb4 in human cells and tissues has not been previously found with the exception of the presence of a small quantity of Forssman glycolipid in some tissues in the human population (Fs+ group) and in some human cancers. The latter four glycolipids (b-e), with the common internal structure R leads to 3GalNAc beta 1 leads to 3Gal alpha 1 leads to 4R', were all reactive to a monoclonal antibody directed to the 4- to 8-cell stage of murine embryos, known as the stage-specific embryonic antigen 3 (SSEA-3 (Shevinsky, L. H., Knowles, B. B., Damjanov, I., and Solter, D. (1982) Cell 30, 697-705]; structure (c) showed the strongest reactivity. These findings, together with the demonstration of the glycolipid nature of SSEA-1 antigen (Kannagi, R., Nudelman, E., Levery, S. B., and Hakomori, S. (1982) J. Biol. Chem. 257, 14865-14874), indicate that cell surface glycolipids play significant roles as differentiation antigens during the course of embryogenesis.